Do we underestimate and downplay how Great Sacramento weather really is? (Los Angeles: crime rate, bars)

[tstieber]

Originally Posted by Chimérique

Hey tstieber , good to hear from you

Sacramento got some lighting, thunder and rain last night. I had puddles of water accumulate in the back porch, backyard but none in the front of the house, go figure.

Sept 10, 2021; 10:30 AM, late morning

Sacramento 69F

San Diego 82F (heat index/feels like temp)
Salt Lake City 83F
Fresno 84F
Las Vegas 96F
Tucson 97F

What a nice cool down NorCal got to enjoy the last couple of days after that Labor Day Heat. I'll bet the actual temperature in my part of San Diego at 10:30 a.m. was even hotter than 82. Downtown by the water seems to top out around the low 80s everyday, but we've been into the low 90s with some monsoonal humidity, but not nearly as bad as some years past. We did, however, watching amazing thunder and lightning storm from our backyard on Thursday nights. It was about 10 miles to our South and moving from east to west, then hooked North into u t c and La Jolla, which is just a short drive directly west of us. We got absolutely no rain in our neighborhood, while other people got drenched if they were in the path of the thunderstorm cell. So we sat out by the pool and watch that lightning storm drift by The Horizon. It was a really great lightning storm!

No big heat waves in store for California for the next 10 days, in fact it should be cooling off nicely later next week. Fall is always a crapshoot in terms of being mild or having terrible fire weather. Cheers, and enjoy the beautiful weekend.

[tstieber]

Random West Coast late summer night temps at 11 PM EST:

Sacramento 70
San Francisco 58
Walnut Creek 65
San Diego Airport 65
San Diego (Scripps Ranch) 61
Los Angeles 59
Fresno 77
Roseville 74
Bakersfield 82
Portland 58
Seattle 56
Reno 65
Las Vegas 88
Palm Springs 91

For many of us, starting to feel a bit like fall with the cooler nights, which is such a treat. Enjoy!

[Chimérique]

Originally Posted by tstieber

Random West Coast late summer night temps at 11 PM EST:

Sacramento 70
San Francisco 58
Walnut Creek 65
San Diego Airport 65
San Diego (Scripps Ranch) 61
Los Angeles 59
Fresno 77
Roseville 74
Bakersfield 82
Portland 58
Seattle 56
Reno 65
Las Vegas 88
Palm Springs 91

For many of us, starting to feel a bit like fall with the cooler nights, which is such a treat. Enjoy!

As you know the best time on the coast is usually Sept/Oct because the marine layer backs off or is not present at all. The impact to Sacramento is no Delta Breeze so Sacramento stays warmer later into the night and the morning temps are not as cool.

But two things mitigate for the lack of a Delta Breeze in Sept/Oct: Shorter days (less sun); and less chance of a full on heat wave caused by a high pressure system trapping in hot air.

This also is the time of the year for more onshore conditions and north winds coming straight down the Sacramento Valley which is usually not a good thing.

In decades past the north wind was not so bad because it usually did not come until at least a few good northern pacific rain storms hit so it wasn't so dry when the north wind cometh. It simply dried things out until the next rain storm, now it spells firestorm for much of NorCal. Fingers crossed we have no new big fires this year.

[shelato]

Originally Posted by Chimérique

As you know the best time on the coast is usually Sept/Oct because the marine layer backs off or is not present at all. The impact to Sacramento is no Delta Breeze so Sacramento stays warmer later into the night and the morning temps are not as cool.

But two things mitigate for the lack of a Delta Breeze in Sept/Oct: Shorter days (less sun); and less chance of a full on heat wave caused by a high pressure system trapping in hot air.

This also is the time of the year for more onshore conditions and north winds coming straight down the Sacramento Valley which is usually not a good thing.

In decades past the north wind was not so bad because it usually did not come until at least a few good northern pacific rain storms hit so it wasn't so dry when the north wind cometh. It simply dried things out until the next rain storm, now it spells firestorm for much of NorCal. Fingers crossed we have no new big fires this year.

Can you unpack that a little more? I was kind of counting on the delta breeze to clean up the smoke locally.

But the specific mechanism of the Delta Breeze is a little unclear to me. The past several days have been pretty hot like a lot of the summer instead of the cooler much more mild fall temperatures that we tend get in mid Oct. I was under the impression that the inland hot air during the day and the temperature gradient between the the valley and ocean primed the pump that started pulling cooler air in from the coast creating the Delta Breeze. But as the days got shorter, and the temperatures inland cooled, shrinking the temperature graident that also killed the Delta Breeze.

But it sounds like I am wrong here.

Second do you actually know why we have the persistent high offshore during the summer time that stops being persistent in the winter time? I mean the National Weather Service tweeted on Sept 10th that the last measurable rainfall we had in downtown Sacramento occurred March 19, 2021. The weather reports always talk about a high pressure system blocking storms from coming into the area, during the summer time, but they don't really explain why that occurs in the summer time but the not the fall, winter or summer. So that too is kind of a black box for me as to why that actually happens.

[Chimérique]

Originally Posted by shelato

I was under the impression that the inland hot air during the day and the temperature gradient between the the valley and ocean primed the pump that started pulling cooler air in from the coast creating the Delta Breeze. But as the days got shorter, and the temperatures inland cooled, shrinking the temperature graident that also killed the Delta Breeze.

You are correct about the temperature gradient on why it pulls in the cool coastal air in the spring/summer.

In the very late summer/early fall, the temperature gradient isn't as pronounced because:
1. NorCal Coastal-ocean upswelling is not as strong.
2. The heating up of the Valley is lessened because there are fewer hours of full sun.

The net effect is the NorCal coast is warmer in the very late summer/early fall than the summer.

The net effect is the Valley is only slightly cooler than the summer during the day, but slightly (surprisingly) warmer (average 4-5 degrees warmer) at night and in the morning because of the absence of the Delta Breeze. As fall progresses the shorter days will be enough to make the days, nights and mornings consistently and significantly cooler than the summer. By mid fall, The Delta Breeze is no longer present but we don't need it to cool us because of the shorter days aren enough to give us cool nighttime and morning temps.

Then the rain storms start usually after Halloween Oct 31 like clock work. But we all know that has not been the case in the last 3-5 years. Usually, Sacramento had at least once decent and coldish rain storm in mid/late Oct, and a few in November, but its been awhile since we've seen that and our last two Halloweens if memory serves correctly were down right warmish.

More on the Delta Breeze:

"The water along the coast of California is cold for a couple of reasons. First, the California Current brings cold water from Alaska southward along the coast. And second, cold water from the deep ocean comes up to the surface through a process called upwelling. From March through September, wind blows southward along the coast. This wind, combined with the rotation of the earth, creates surface currents that move water from the coast out into the ocean. Something has to fill in the space that was left behind when the surface waters moved out to sea. So water from the deep ocean is sucked to the surface. And the water from the deep ocean is really cold, which makes fog form over the areas of upwelling.
The fog rolls in from the ocean onto land in the morning as the rising sun heats up the land. Warm air rises, and something has to fill its place—the foggy air that’s hanging out above the ocean.

So to summarize, summer winds create upwelling, fog forms over the cold water, summer sun heats the air above the land and makes it rise, and the fog gets sucked in." From a SF article.

[shelato]

Thanks for the very detailed explanation. I really do appreciate that.

[Chimérique]

Originally Posted by Chimérique

In the very late summer/early fall, the temperature gradient isn't as pronounced because:
1. NorCal Coastal-ocean upswelling is not as strong.
2. The heating up of the Valley is lessened because there are fewer hours of full sun.

The net effect is the NorCal coast is warmer in the very late summer/early fall than the summer.

The net effect is the *Valley* is only slightly cooler than the summer during the day, but slightly (surprisingly) warmer (average 4-5 degrees warmer) at night and in the morning because of the absence of the Delta Breeze. As fall progresses the shorter days will be enough to make the days, nights and mornings consistently and significantly cooler than the summer. By mid fall, The Delta Breeze is no longer present but we don't need it to cool us because of the shorter days aren enough to give us cool nighttime and morning temps.

NOTE CORRECTION IN BOLD


Replace *Valley* with Sacramento

In the very late summer/early fall, the temperature gradient isn't as pronounced because:
1. NorCal Coastal-ocean upswelling is not as strong.
2. The heating up of the Valley is lessened because there are fewer hours of full sun.

The net effect is the NorCal coast is warmer in the very late summer/early fall than the summer.

The net effect is SACRAMENTO is only slightly cooler than the summer during the day, but slightly (surprisingly) warmer (average 4-5 degrees warmer) at night and in the morning because of the absence of the Delta Breeze. As fall progresses the shorter days will be enough to make the days, nights and mornings consistently and significantly cooler than the summer. By mid fall, The Delta Breeze is no longer present but we don't need it to cool us because of the shorter days aren enough to give us cool nighttime and morning temps.

[tstieber]

8 PM temps on the last day of summer:

Sacramento 84
Fresno 84
Redding 84
SF 69
Walnut Creek 82
San Jose 80
Santa Cruz 62
Reno 73
Portland 72
Seattle 65
San Diego 75
SD (Scripps Ranch) 77
LA 77
Santa Barbara 66
Irvine 79
La Jolla 72

Perfect night!

[Chimérique]

^ Like I said before, Sacramento's Delta Breeze is not present or has little impact in the late summer, early fall. If it were not for the shorter days, late summer, early fall would some of the warmest weeks of the year for Sacramento.

Last night 8pm

You forgot:

Phoenix 92F
Vegas 85F
Tucson 84F
Sacramento 84F

Forecast low for this morning:

Phoenix 77F
Sacramento 62F - and this is without the Delta Breeze. When the Delta Breeze was present last week the lows were in the mid 50's.

[Valley Boy]

Indian summer right now. Where the lingering heat of summer tries to make a last hurrah every now and then.

Hopefully we get some good rain coming up north to put out those fires, or another northwind is gonna smoke us out.